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The existing study examines the moisture-dependent vibrational behavior of a metal foam spherical panel that is positioned between two composite layers reinforced with graphene platelets (GPL). The Kerr foundation, a three-parameter elastic foundation, supports the model. Based on specified functionalities, the pores’ arrangement and the GPL dispersion throughout the core and face sheets, respectively, are taken into consideration. The Halpin–Tsai and extended rule of mixture micromechanical models are utilized to ascertain the face sheets’ effective hygromechanical property values. After the motion equations are determined, the frequencies are extracted using the analytical technique, which is particularly effective for shells with simply supported edges. The impacts of various influences on the natural frequencies are considered and addressed over the course of the inquiry. It is shown that natural frequencies drop with increasing porosity coefficient. Furthermore, a small amount of GPL is shown to have a strong reinforcing effect on the stiffness of the structure, hence enhancing natural frequencies. The outcomes of this investigation can be beneficial to a variety of industries such as aerospace, automotive, marine, and civil engineering, where spherical shells are commonly employed. Furthermore, the outcomes might function as a standard for subsequent research. These results not only advance the understanding of moisture effects on composite structures but also provide a foundation for future research aimed at optimizing material properties for specific applications. Additionally, this study offers practical insights for the design and manufacturing of more resilient and efficient spherical components in real-life engineering scenarios.

This paper is concerned with the load-carrying capacities of a circular sandwich panel with metallic foam core subjected to quasi-static pressure loading. The analysis is performed with a newly developed yield criterion for the sandwich cross section. The large deflection response is estimated by assuming a velocity field, which is defined based on the initial velocity field and the boundary condition. A finite element simulation has been performed to validate the analytical solution for the simply supported cases. Good agreement is found between the theoretical and finite element predictions for the load-deflection response.

The Sierpinski fractal is introduced to construct the porous metal foam. Based on this fractal description, an unsteady heat transfer model accompanied with solidification phase change in fractal porous metal foam embedded with phase change material (PCM) is developed and numerically analyzed. The heat transfer processes associated with solidification of PCM embedded in fractal structure is investigated and compared with that in single-pore structure. The results indicate that, for the solidification of phase change material in fractal porous metal foam, the PCM is dispersedly distributed in metal foam and the existence of porous metal matrix provides a fast heat flow channel both horizontally and vertically, which induces the enhancement of interstitial heat transfer between the solid matrix and PCM. The solidification performance of the PCM, which is represented by liquid fraction and solidification time, in fractal structure is superior to that in single-pore structure.

The fractal geometry provides a new insight for the description for actual pore structure of metal foams. In this paper, the fractal grids are introduced to describe the pore structure of metal foams. A two-dimensional unsteady melting model of phase change material (PCM) in the cross-fractal metal foam is developed and numerically simulated. The transient temperature variation and melting front evolution during the charging process in the cross-fractal metal foam are analyzed. The effects of initial temperature difference, porosity and fractal dimension on the melting heat transfer in fractal metal foam are examined and analyzed. The results indicate that the temperature distribution is more uniform and the melting rate is faster in the cross-fractal metal foam compared with that in the corresponding cavity structure. Interestingly, the fractal metal foam with smaller fractal dimension provides a faster heat flow path and hence enhances the melting performance though the porosity is identical. The melting performance in fractal metal foam can be enhanced when the metal foams have a lower porosity, a smaller fractal dimension and a larger initial temperature difference.

A novel and simple approach for preparing nanoporous binder free Sn:Pb composite metal foam has been demonstrated. The anodized metallic composite block was functionalized and also found a nanoporous structure. A scanning electron microscopy (SEM) result shows that the nanoflake-like arrangement has synthesized. The X-ray diffraction (XRD) results confirm the nanoporous structure of the Sn/Pb foam after etching with 6 M NaOH. The prepared Sn:Pb metal foam is able to be used as a super capacitors electrode to offer large areal capacitance with regards to the synergic integration of Sn and Pb metals and the unique nanoporous structure.

This paper presents the low-velocity impact tests on the sandwich plates with aluminum foam core and aluminum skins at elevated temperatures. A furnace, attached to an Instron Dynatup 9250 HV drop hammer system, was designed to accomplish the penetration tests at temperatures up to 500°C. In order to process the experimental data accurately, the numerical vibration analysis was conducted to determine the threshold frequencies of the fast Fourier transform (FFT) filter for the original impact data. The experimental results showed that the failure modes of the sandwich, peak load and absorbed energy varied obviously with temperatures. Furthermore, the results showed that the failure modes of the top skin and metal foam core showed minor changes with respect to temperatures. Whereas the failure mode of the bottom skin and peak loads changed significantly with respect to temperatures. Also, the absorbed energy revealed a three-stage variation with the change of temperature.

The surging interest in porous lightweight structures has been witnessed in recent years to pursue material innovations in broad engineering disciplines for sustainable developments and multifunctional proposes. Functionally graded (FG) porous composites represent a novel way to adjust mechanical characteristics by controlling the porosity distributions. However, the further advance in this field is challenged by the scale gap between mesoscopic and macroscopic aspects of porous structural analysis, i.e. how the local cellular morphologies impact the overall behaviors. The purpose of this paper is to bridge this gap by conducting a theoretical investigation on the performance of inclined self-weight sandwich beams with FG porous cores, where Young’s modulus is obtained with representative volume elements (RVEs) in a multiscale modeling study and depends on the cellular morphologies: average cell size and cell wall thickness. The material properties of closed-cell steel foams are adopted in a two-step assessment on target beams, including a static calculation to examine their bending deformations under gravitational loading which are then imported into a forced vibration analysis considering constant and harmonic moving forces. Timoshenko beam theory is used to establish the displacement field, while Ritz and Newmark methods are employed to solve the governing equations in terms of bending, free vibration, and forced vibration. The inclined beams are assumed to rest on a Pasternak foundation, and the corresponding structural responses can be determined based on the specific cell size and cell wall thickness, of which the effects are quantitatively revealed: the stiffness degradation induced from cellular morphologies increases the dynamic deflections, while the corresponding self-weight static deformations are reduced and the fundamental natural frequencies are raised. The influence from geometrical, boundary, and foundation conditions is also discussed to provide a comprehensive overview. This will be valuable for engineers to develop devisable foam-based load-carrying components with enhanced properties.

Metal foams are highly useful in industries because of their lightweight, energy and vibration absorption properties. This study investigated the propagation of torsional waves in an elastic layer over a fluid-saturated fractured poroelastic half-space with a metal foam coated layer. It is assumed that the interfaces are in sliding contact with two different sliding parameters. The coated layer is closed-cell aluminium foam. We use the separation variable technique and the Bessel function to solve the equation of motion in different layers. The displacement components are written in terms of the second kind Whittaker functions. Using an asymptotic formulation of the Whittaker function and appropriate boundary conditions, the dispersion equation is derived in terms of the determinant. The control of the vibration due to the metal foam-coated layer is one of the important goals of this study. Also, numerical and graphical analyses have been done with the help of Mathematica software to see the effect of different parameters on torsional wave propagation. It is found that the presence of coated metal foam layer decreases the phase velocity of the torsional wave propagation. The work may be helpful in the seismology, automobile, and aerospace industries.

In this study, two kinds of dynamic compression tests were conducted using direct-impact Hopkinson pressure bar (DHPB) facilities, i.e., the bullet with foam specimen was shot on the transmission bar, or the foam specimen was mounted at the end surface of the transmission bar and was hit by a bullet directly. Stress enhancement and localized deformation, as two mainly dynamic properties of metal foam, were observed in the experiments. Then, dynamic locking strain is proposed in order to better describe the feature of foam’s localized deformation field during the impact process. A rigid- perfectly-plastic-dynamic-locking strain model (R-P-P-D-L model) is developed to study the dynamic properties of the foams. The parameters included in this model are determined by 3D numerical Voronoi model and experiments. Comparing the predictions from R-P-P-D-L model with numerical results and experimental results, it is found that the R-P-P-D-L model can capture the main deformation mechanisms of the foam in dynamic compression, and provide a more precise prediction than R-P-P-L model. Furthermore, the stress enhancement of foam with the relative density and the impact velocity are discussed using the R-P-P-D-L model.

Large-deflection bending of fully clamped slender metal foam-filled rectangular tubes is investigated theoretically, experimentally and numerically. A plastic yield criterion for the foam-filled rectangular tube is proposed. Considering the filled foam strength effect and the interaction of bending and stretching, an analytical solution is proposed to predict the structural response of the foam-filled rectangular tubes transversely loaded by a flat punch. Clamped bending tests of aluminium alloy foam-filled rectangular tubes are conducted. The analytical model captures experimental results reasonably. Numerical calculations are carried out to predict the large-deflection behavior of the foam-filled tubes, and good agreement is achieved between the analytical solutions and numerical results. The effects of wall thickness of tube, punch size and filled foam strength are discussed in detail. It is demonstrated that the present analytical model can reasonably predict the post-yield behavior of the foam-filled rectangular tube.

Split Hopkinson pressure bar (SHPB) technique is the most important test method to characterize dynamic stress–strain relations of various materials at different strain rates, and this technique requires uniform deformation of specimen during the experiment. However, some studies in recent years have found obvious deformation localization within metal foam specimens in SHPB tests, which may significantly affect the reliability of the results. Usability of SHPB to characterize dynamic stress–strain relation of metal foam becomes doubtful. In this paper, based on experimental verification, we carried out numerical simulative SHPB tests to study the problem, in which the metal foam specimens were modeled to have 3D meso structures with properties of their matrix material. Numerical simulative SHPB tests of aluminum foam specimens with varying thickness at different strain rates were performed. Deformation distribution in each local region of the specimen was examined and a concept of “effective specimen” was presented. Appropriate specimen thickness and range of testing strain rate were suggested based on quantitative analysis. Finally, we recommended a method how to revise the nominal strain and strain rate measured by traditional SHPB method to acquire the reliable dynamic stress–strain relation.

In this paper, the dynamic response of clamped rectangular sandwich tubes with metal foam core under transverse blast loading is analytically and numerically studied. First, based on the theory of the solid beam subjected to transverse blast loading, a semi-empirical analytical solution for the dynamic response of rectangular hollow metal tube is given subjected to transverse blast loading considering local denting effect and combined axial force and bending moment. Then, based on the analytical solution for the dynamic response of the metal tube, a semi-empirical analytical solution for the dynamic response of clamped rectangular sandwich tubes with metal foam core under transverse blast loading is obtained. The numerical calculation for the dynamic response of clamped rectangular sandwich tubes is carried out. The numerical results locate between the upper and lower bounds of the analytical solution. Next, using the least square method, an analytical method to predict the maximum deflection of sandwich tubes is given under no experimental or numerical data conditions based on the existing data. The present analytical method can be used to predict the dynamic response of clamped rectangular sandwich tubes with metal foam core under transverse blast loading. Also, the comparison of energy absorption between rectangular sandwich tube with metal foam core and rectangular hollow tube for the same mass is conducted. It is shown that the sandwich tube is better than the hollow tube in terms of energy absorption in large deflection.

The development of high-performance heterogeneous catalysts is critical to meet the industry decarbonization goals due to their easy separation from the reaction media and reusability. In heterogeneous catalysis, the reaction takes place at the surface level. Thus, the active area of the catalyst is critical to the extent of determining its final activity. For that reason, the preparation of porous materials, in particular 3D architectures with highly accessible surface area and reaction centers, is a cornerstone of heterogeneous catalysis. Among the methods employed to prepare large-surface 3D materials, synthesis based on electrochemical methods stand out due to their low cost and minimal environmental impact, their safety and their adaptability. Electrochemical techniques can be used to obtain large active-surface materials with controlled surface properties (composition, morphologies, etc.). Therefore, electro-chemical synthesis and engineering are becoming valuable tools for the mass production of porous catalysts. This chapter overviews the efforts reported in the literature to prepare porous catalysts by electrochemical techniques. These are also described in the context of a broad range of applications, from renewable energy to the removal of pollutants. A brief explanation of the fundamental principles of electrochemical synthesis introduces an overview of the different electrochemical synthesis used to prepare high-surface materials. To conclude, the main applications of these materials are discussed.

This paper is concerned with the load-carrying capacities of a circular sandwich panel with metallic foam core subjected to quasi-static pressure loading. The analysis is performed with a newly developed yield criterion for the sandwich cross section. The large deflection response is estimated by assuming a velocity field, which is defined based on the initial velocity field and the boundary condition. A finite element simulation has been performed to validate the analytical solution for the simply supported cases. Good agreement is found between the theoretical and finite element predictions for the load-deflection response.